Skip to main content

1903 - Largest Odd Number in String (Easy)

https://leetcode.com/problems/largest-odd-number-in-string/

Problem Statement​

You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring ofnum, or an empty string""if no odd integer exists.

A substring is a contiguous sequence of characters within a string.

Example 1:

Input: num = "52"
Output: "5"
Explanation: The only non-empty substrings are "5", "2", and "52". "5" is the only odd number.

Example 2:

Input: num = "4206"
Output: ""
Explanation: There are no odd numbers in "4206".

Example 3:

Input: num = "35427"
Output: "35427"
Explanation: "35427" is already an odd number.

Constraints:

  • 1<=num.length<=1051 <= num.length <= 10 ^ 5
  • num only consists of digits and does not contain any leading zeros.

Approach 1: Retain from last odd number​

A number is odd as long as the last digit is odd. Therefore, we can search the last odd digit in the string and build the substring.

Written by @wingkwong
class Solution:
    def largestOddNumber(self, num: str) -> str:
        last = -1
        for i in range(len(num)):
            if int(num[i]) & 1:
                last = i
        return num[:last + 1]